Towards intelligent dual-comb lasers: automatic bidirectional mode-locking via genetic algorithm

Bidirectional mode-locked fiber lasers have recently attracted intense research interest for dual-comb spectroscopy applications. However, achieving stable bidirectional single-pulse mode-locking typically requires careful manual adjustment of laser parameters such as birefringence and pump power, owing to the interactions and competitions between the counter-propagating pulses. In this work, we demonstrate, for the first time to the best of our knowledge, an automatically mode-locked bidirectional soliton fiber laser. A gold nanofilm based saturable absorber, featuring a high damage threshold and good long-term stability, is employed to initiate mode-locking. An iterative multi-stage genetic algorithm is developed to realize automatic mode-locking. The algorithm utilizes only the dispersive Fourier transforms of the bidirectional output pulses to construct the fitness function. Furthermore, a feedforward neural network integrated within the algorithm enables accurate identification of bidirectional single-pulse operation. This work opens new avenues for developing intelligent dual-comb light sources.